“双元结构”盆地油气成藏的特点——以车镇凹陷第三系为例

车镇凹陷第三纪盆地是在前第三系基岩背景上经构造运动发育起来的断陷-坳陷湖盆,经历了早第三纪裂陷沉降和晚第三纪-第四纪坳陷沉降两个阶段,从而形成具有双层次岩相组构的盆地.下层系油源层发育,断裂发育,热演化油气成藏机制的控油规律明显,上层系油源层不存在,断裂不发育,油气只有通过连通上下层系的输导体系,才能进入到上层系聚集成藏.根据油气运移聚集的特点,油气成藏模式主要有两种:一是下第三系的"自生自储"型原生油气藏,二是上第三系和第四系的"下生上储"型次生油气藏.

CHARACTER OF OIL-GAS ACCUMULATING IN DOUBLE-LAYER STRUCTURE BASINS-TAKING TERTIARY IN CHEZHEN SAG AS AN EXAMPLE

Chezhen sag is a Tertiary fault-depressed basin with of pre-Tertiary basement. Its evolution can be divided into two stages, Palaeogene rifting subsidence and Neogene and Quaternary depression subsidence. It is a basin with double-layer lithofacies structure. Source beds and fault system are full development in lower layer. Rule of oil-gas control is related with thermal evolution formed pool mechanism. Source beds and fault system are less development in upper layer. Oil-gas formed in lower layer went up though passage system which connects the upper layer and lower layer. Based on character of migrating and accumulating, two oil-gas pool mode has been set up: one is Eogene autogeny and auto-accumulation primary reservoir in the lower layer; the other is Neogene and Quaternary hypogeous pool in lower layer and shallow-accumulation secondary reservoir in the upper layer.